1. Field of the Invention
The present invention relates to an image pickup optical system and an image pickup apparatus using the same.
2. Description of the Related Art
In recent years, with slimming of a portable telephone and a portable terminal, or a notebook-size personal computer, a camera module in which, a length of an optical system in an optical axial direction is reduced to the utmost limit has been sought. In order to fulfill the need, a large number of single-focus optical systems which include two to three aspheric lenses have been proposed.
Moreover, in recent years, with the advancement of technology related to an image pickup element, and with increasing needs of the market, a low-cost camera module with a large number of pixels and a wide angle, while being small-size, has been sought. As an optical system in which, shortening of an overall length has been facilitated while improving an image forming performance, a single-focus optical system which includes four lenses has been proposed (Japanese Patent Application Laid-open Publication Nos. 2008-158413 and 2008-268946)